Electrostatic toner head and system



Sept. 19, 1967 A. M. LEWIS ELECTROSTATIC TONER HEAD AND SYSTEM 2Sheets-Sheet 1 Filed Nov. 4, 1964 INVENTOR. ARTHUR M.LEWI$ BY 540%WiATTORNEY Sept; 19, 1967 A. M. LEWIS 'ELECTROSTATIC TONER HEAD AND SYSTEMFile d Nov. 4, 1964 2 Sheets-Sheet P,

"iii-i INVENTOR.

ARTHUR M LEWIS ATTOEY United States Patent 3,342,164 ELECTROSTATIC TONERHEAD AND SYSTEM Arthur M. Lewis, Shaker Heights, Ohio, assignor toClevite Corporation, a corporation of Ohio Filed Nov. 4, 1964, Ser. No.408,894 7 Claims. (Cl. 118-637) This invention pertains to a system andapparatus for applying liquid toner to a record medium to develop thelatent electrostatic image thereon.

Liquid toners have been used to develop latent electrostatic images buthave not generally been highly acceptable compared to dry powderdevelopers because of the presence of excess liquid toner on the recordand because of the time necessary to dry the record.

Liquid toners, if the extended drying time can be reduced, have someadvantages over the dry powder toners.

In the past attempts have been made to reduce the time necessary to drythe liquid toners by squeezing excess liquid off the record withrollers, or by spraying a controlled small amount of liquid toner on therecord, followed in both instances by final drying in hot air. Whilethese systems have already achieved some commercial success in devicesfor copying whole sheets of records, neither system is sufiicientlyrapid to permit its use in direct writing oscillograph devices.

A direct writing oscillograph should be able to drive the record mediumpast the recording stylus at selected speeds between very low speeds andvery high speeds, and it must develop the latent image sufficientlyrapidly that the record becomes almost immediately visible.

It is an object of the present invention to provide an applicator systemfor applying liquid toner to a record member on which a latentelectrostatic image has been recorded, wherein relatively largequantities of toner are applied to the record, and wherein all excesstoner is quickly removed after the image has been developed tofacilitate rapid drying of the record.

Another object of the invention is to provide a liquid toner system forrapidly developing and substantially drying a moving record chart.

Still another object of the invention is to provide a toner head forapplying liquid toner to a rapidly moving electrostatic record chart andfor removing the excess liquid toner therefrom.

For a better understanding of the present invention, together with otherand further objects thereof, reference is had to the followingdescription taken in connection with the accompanying drawings, and itsscope will be pointed out in the appended claims.

The broad term electrostatic recording may embrace xerography,electrographic recording and other systems. The present invention dealswith those electrostatic systems wherein a latent or invisible record ismade on a record member, which latent image is thereafter developed bythe application of toner.

An example of the xerographic process is described in Carlson Patent2,297,691, issued in 1942. Liquid toner development of a stationaryrecord is described in Patent 3,129,115 issued to Clark et al. in 1964.

An aspect of the present invention lies in the provision of anapplicator system and a toner head therefor, for applying liquid tonerto a record medium on which a latent electrostatic record has beenrecorded. A housing forms with the record medium a developer compartmentthrough which quantities of liquid toner are circulated in contact withthe surface of the record medium. One or more cleaning nozzles areadjacent the surface of the record medium, and preferably the cleaningnozzles are adjacent the developer compartment, for withdrawing3,342,164 Patented Sept. 19, 1967 from the surface of the record mediumall excess liquid toner.

With respect to the drawings there is shown in:

FIGURE 1 a view of a direct writing oscillograph embodying the presentinvention.

FIGURE 2 is a view of the toner head.

FIGURE 3 is a view of the toner head with a front plate removed to showthe interior thereof.

FIGURE 4 is a sectional view taken along line 44 of FIGURE 2.

FIGURE 5 is a sectional view taken along line 55 of FIGURE 2.

FIGURE 6 is a view of a modified type of a toner head with its frontplate removed.

FIGURE 7 is a side view of the device shown in FIG- URE 6, and

FIGURE 8 is a sectional view taken along line 88 of FIGURE 7.

With reference to FIGURE 1 there is shown a direct writing oscillographmounted on a base 10, the cover therefor being removed. The oscillographcomprises an electromagnetic device 12 which oscillates a recordingstylus 13 in accordance with an electric signal applied from a source 14to terminals 15, 16, as is known in the art. The stylus 13 applies anelectrostatic latent image to a moving strip of record medium 17 whichis driven at any one of a large number of selected speeds by motormeans, gears and the like, the details of which form no part of thisinvention.

The stylus 13 is connected to a source 20 to provide the recordingvoltage. For example, the source 20 may apply 500700 volts DC. of eithernegative or positive polarity.

After the latent signal image has been applied to the moving recordmedium 17 the strip passes under a toner head 21 where liquid toner isapplied to the surface of the record medium to make the latent imagevisible. Liquid toners per so are well known to the art.

The toner head 21 preferably is mounted in a closed liquid circulatingsystem which comprises a reservoir 25 containing the liquid toner 26. Anoutlet pipe 23 from the reservoir 25 is connected to the inlet 27 of thetoner head 21, and the outlet 28 of the toner head 21 is connected byhose 29 to the inlet of pump 30 which is driven by motor 31. The outletof pump 30 is connected by hose 32 to the reservoir 25 for returning theexcess liquid toner and any air picked up by head 21 thereto. A vent 24is provided in reservoir 25 to vent the excess air which may be pumpedinto the reservoir along with excess liquid toner.

It 'is important that the pump 30 be connected to the outlet side 28 ofthe toner head 21 so that it applies a partial vacuum to the toner head21. The record medium 17 is directly under the toner head 21, and, asshown best by FIGURE 4, the record medium effectively seals severalopenings 33 and a developer compartment 34 in one face 35 of the tonerhead 21. The partial vacuum established by pump 30 pulling the liquidtoner 26 through the toner head 21 holds the record member 17 up againstthe underneath face 35 of the toner head. This effectively seals theopenings 33 and 34 therein, and it prevents the liquid toner which iswithin the toner head from escaping from the toner head.

The toner head is show in detail in FIGURES 2 to 8. In FIGURES 2 and 3it is upside down compared to its position in the instrument shown inFIGURE 1, and in FIGURE 3 a plate has been removed to show the interior.An advantage of the present system and head is that it will operate inany position.

The toner head 21 is comprised of a housing 40- which is hollow andwhich has an opening 41 at its face 35.

Within the housing 40 there is a small chamber 52 formed by walls 44, 45spaced from the side walls 46, 47 of the housing. As shown in FIGURE 4the walls 44, 45 do not extend as far down as do the side walls 46, 47.A face plate 50 having an opening 53 is secured by screws 51 in theopening 41 so that it encloses the chamber 52 and provides communicationwith the developer compartment 34. The face plate 50 has two smallopenings 54 at its end opposite to the opening 53. Inlet pipe 27communicates with chamber 52 so that liquid toner flows through chamber52. Opening 53 in plate 50 permits toner fluid in chamber 52 to flowinto the developer compartment 34 located between the record medium 17and the face plate 50, and the liquid toner flows through the two smallopenings 54 back into a passageway 60', and from there it flows out theoutlet pipe 28 to the pump 30. Thus only a very small volume of toner isactually against the surface of the record medium at any given time sothat if the supply of paper is exhausted virtually no toner is spilledif the liquid surface in the reservoir is at a level below the head.This avoids a siphon action which otherwise might take place. Because ofthe crosssectional area of the compartment 34 and because of the flow oftoner through it, the surface of the record medium 17 under the head 21is in intimate contact with a sufficient volume of continually replacedtoner.

Face plate 50 preferably is made of metal and compartment 34 is veryshallow so that its side 36 is close to the surface of the record medium17 while developing the latent image. This closely spaced conductingsurface 36 acts as a developing electrode to speed up development.

The face plate 50 almost, but not completely, closes the opening 41 inthe face 35 of the toner head 21, thereby forming with the side walls ofthe housing one or more long narrow openings or nozzles 33. Preferably along narrow opening 33 is located at each side of the developercompartment 34 where toner is applied to the record medium, though it ispossible to satisfactorily operate the toner head with only one suchslot 33 if it is located to the side of the head toward which the recordmedium is moving; i.e. to the right hand side in FIGURE 4. Compartment60 is in communication with these slots 33, and compartment 60 isconnected to the outlet pipe 28 so that pump 30 establishes a negativepressure therein. Excess liquid toner that escapes from the developercompartment 34 is vaccumed up into the compartment 60 and is thenreturned to the reservoir 25 together with any air which leaks inbetween the walls 46, 47 and the record medium 17. This negativepressure or partial vacuum at the slots 33 to either side of the head 21assures that the record medium Will engage the face 35 of the head tominimize liquid leakage from the developer compartment 34. Thus thepartial vacuum in compartment 60 and in the slots 33 serve a dualpurpose-4o hold the record medium against the face 35 of the head 21 andto vacuum up any excess liquid toner.

Holes 54 are deliberately made restrictive to toner flow thereby toestablish a pressure differential between compartments 34 and 60. Thispressure differential prevents :air from leaking into the developercompartment 34, and assures that during normal operation the developercompartment 34 will at all times be full of toner liquid.

The developed record is in an essentially dry state as 'it leaves thehead since the liquid toner contacts only one face of the record for anextremely short interval of time and since excess liquid toner isimmediately vacuumed up from the surface of the record medium. Therecord is made visible almost immediately, and the oscillograph does nothave to provide a long loop in which the record is heated to facilitatedrying.

An alternative head is shown in FIGURES 6 to 8. In this embodiment thetoner head 21 has an inlet pipe 27' and an outlet pipe 28'. Liquid tonerand air are pulled out of outlet pipe 28' by a pump 39 therebyestablishing the essential partial vacuum within the head, and liquidtoner is pulled into the inlet pipe 27. Additionally a pipe 65 isconnected to the pump 30 to circulate the spent liquid toner and returnit to the reservoir. The pipe 65 extends through the head 21' andthrough the face plate into the compartment 34 where the developingprocess takes place. The compartment 60 which is formed in the head 21',and grooves 68 in the side walls of the head communicate at a number oflocations with the slots 33'. Any excess liquid on the record isvacuumed up by slots 33' and passes through grooves 68 into thecompartment 60 and is then returned through pipe 28 to the reservoir.

Pipe 65 is connected to the pump 30 through restrictive means whichestablish the pressure differential between compartments 34' and 60'.The restrictive means may merely be a long, small pipe or it may includea throttle valve.

The flow path of the liquid toner, as best shown in FIG- URE 7, is frominlet pipe 27 into compartment 52', thence through orifice 53' into thedeveloper compartment 34', and then out through pipe 65 to the pump 30,as shown by the arrows 67. Any liquid tone-r which escapes from thedeveloper compartment 34 is vacuumed up by nozzles 33' and passesthrough grooves 68 into compartment 60', together with any air whichflows into the head between the record 17 and the side walls 46', 47'(as shown by arrows 69), and the mixture is exhausted out through pipe28 by pump 30 and is returned to the reservoir.

While there have been described what are at present considered to be thepreferred embodiments of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and it is, therefore,aimed in the appended claims to cover all such changes and modificationsas fall within the true spirit and scope of the invention.

I claim:

1. An applicator system for applying liquid toner to a record medium onwhich a latent electrostatic record has been applied, comprising, ahousing forming with said record medium a substantially closed developercompartment, circulator means for circulating liquid toner through saidcompartment and against a surface of said record medium to develop saidlatent record, said circulator means including a reservoir for saidliquid toner, means connecting said reservoir to said housing in aclosed liquid circuit, means for circulating said toner through saidclosed circuit and for applying a partial vacuum to said compartment,air suction means including cleaning nozzle means separated from saiddeveloper compartment and within said housing and adjacent the surfaceof said record medium for withdrawing from the surface of said recordmedium excess liquid toner, and means connecting said air suction meansto said circulator means for returning said air and said excess liquidtoner to said reservoir.

2. An applicator system for applying liquid toner to a record medium onwhich a latent electrostatic record has been applied thereby to developsaid record, comprising, in combination, a housing, means for movingsaid record medium in engagement with said housing to establish asubstantially closed developer compartment, a reservoir of liquid tonerconnected to said compartment, pump means connected to said housing andalso connected to said reservoir for withdrawing said liquid toner fromsaid compartment and for returning it to said reservoir and therebyestablishing in said compartment a partial vacuum which tends to holdsaid record medium against said housing, and air suction means includingcleaning nozzle means operated below ambient pressure located adjacentthe surface of said record medium and within said housing forwithdrawing from the surface of said record medium excess liquid toner,said cleaning nozzle means being separated from said developercompartment and being to the side of said compartment toward which saidrecord medium moves after it has been developed.

3. An applicator system for applying liquid toner to a record mediumaccording to claim 2, further characterized by means connecting said airsuction means to said liquid pump means whereby said excess toner andair is returned to said reservoir.

4, An applicator system for applying liquid toner to a record mediumaccording to claim 2, further characterized by cleaning nozzle meansadjacent the surface of said record medium and adjacent both sides ofsaid compartment.

5. A toner head for applying liquid toner to a record medium on which alatent electrostatic record has been applied, comprising, a housinghaving an opening adapted to be closed by said record medium toestablish a developer compartment, means admitting liquid toner to saiddeveloper compartment, means for withdrawing said liquid toner from saiddeveloper compartment thereby establishing within said compartmentpressure below ambient and air suction means including a nozzle formingpart of said housing, said nozzle being separated from said developercompartment and within said housing and adjacent said record medium forwithdrawing from said record medium excess liquid toner.

6. A toner head as set forth in claim 5 further characterized by saidmeans for withdrawing said liquid toner and said air suction means forwithdrawing said excess liquid toner being connected to the same vacuumpump.

7. A toner system for applying liquid toner to a moving record medium onwhich a latent electrostatic record has been applied, comprising, ahousing forming With said record medium a substantially closed developercompartment, means for moving liquid toner through said housing and inengagement with said record medium to develop the latent image thereon,and cleaning nozzle means separated from said developer compartment andWithin said housing and adjacent said record medium at a location wheresaid latent image has been developed, said nozzle operating belowambient pressure at the surface of said record medium to remove excessliquid toner therefrom by vacuuming up the excess liquid.

References Cited UNITED STATES PATENTS 2,242,182 5/1941 McCann 118-415 X3,027,821 4/1962 Wright 11841O X 3,038,442 6/1962 Jones et a1. 118-6373,081,687 3/1963 Takats -89 3,122,453 2/1964 Montgomery 118---6373,176,653 4/1965 Hansen 118-637 3,196,832 7/1965 Zin 118-637 3,238,9213/1966 Engelstad et al 118637 3,277,493 10/ 1966 Fyler.

FOREIGN PATENTS 649,949 10/1962 Canada.

CHARLES A. WILLMUTH, Primary Examiner. PETER FELDMAN, AssistantExaminer.

7. A TONER SYSTEM FOR APPLYING LIQUID TONER TO A MOVING RECORD MEDIUM ONWHICH A LATENT ELECTROSTATIC RECORD HAS BEEN APPLIED, COMPRISING, AHOUSING FORMING WITH SAID RECORD MEDIUM A SUBSTANTIALLY CLOSED DEVELOPERCOMPARTMENT, MEANS FOR MOVING LIQUID TONER THROUGH SAID HOUSING AND INENGAGEMENT WITH SAID RECORD MEDIUM TO DEVELOP THE LATENT IMAGE THEREON,AND CLEANING NOZZLE MEANS SEPARATED FROM SAID DEVELOPER COMPARTMENT ANDWITHIN SAID HOUSING AND ADJACENT SAID RECORD MEDIUM AT A LOCATION WHERESAID LATENT IMAGE HAS BEEN DEVELOPED, SAID NOZZLE OPERATING BELOWAMBIENT PRESSURE AT THE SURFACE OF SAID RECORD MEDIUM TO REMOVE EXCESSLIQUID TONER THEREFROM BY "VACUUMING" UP THE EXCESS LIQUID.